<!doctype html>
<html>
<head>
    <meta charset="utf-8">
    <title>简单易用的倒计时js代码</title>
    <style>
        *{ margin:0; padding:0; list-style:none;}
        body{ font-size:18px; text-align:center;}
        .time{ height:30px; padding:200px;}
    </style>
</head>
<body>
<div class="time">
    <span id="t_d">00天</span>
    <span id="t_h">00时</span>
    <span id="t_m">00分</span>
    <span id="t_s">00秒</span>
</div>
<script>
    function GetRTime(){
        var EndTime= new Date('2017/09/20 00:00:00');
        var NowTime = new Date();
        var t =EndTime.getTime() - NowTime.getTime();
        var d=0;
        var h=0;
        var m=0;
        var s=0;
        if(t>=0){
            d=Math.floor(t/1000/60/60/24);
            h=Math.floor(t/1000/60/60%24);
            m=Math.floor(t/1000/60%60);
            s=Math.floor(t/1000%60);
        }


        document.getElementById("t_d").innerHTML = d + "天";
        document.getElementById("t_h").innerHTML = h + "时";
        document.getElementById("t_m").innerHTML = m + "分";
        document.getElementById("t_s").innerHTML = s + "秒";
    }
    setInterval(GetRTime,0);
</script>

</body>
</html>